Dopefish

The Dopefish is originally an enemy from Commander Keen IV, designed by Tom Hall, a large green fish, prominently bucktoothed, and famous as the second stupidest creature in the universe (the first stupidest being the Ravenous Bugblatter Beast of Traal from Douglas Adams' The Hitchhiker's Guide to the Galaxy book series). Its thought patterns were described simply as "swim, swim, hungry, swim, swim, hungry".

Easter eggs referencing the character were common in Apogee Software games, and have since become an industry wide in-joke. The dopefish itself, or the sentence "dopefish lives!" have appeared in Quake, Quake II, Rage, Daikatana, Anachronox, Duke Nukem 3D, Descent, Kingpin, Max Payne, Deus Ex: Human Revolution, and more.

Doom (2016)

 * An open locker in the Foundry is marked with a dopefish outline.
 * Take-out boxes of "Dopechan Noodles" can be found in various areas of the Mars base.
 * A dopefish with a bowtie is the mascot character of "Grangles potato crisps", a parody of.
 * "Grima"-brand water bottles in vending machines have a dopefish logo.
 * Many other food items have a dopefish outline on the back side of their packaging, including "Diet Grulp" soda bottles and cans, "Dr Bubbles" soda bottles, "Grud Light" beer cans, and "Mudbutt"-brand "chocolate flavored milk, low fat".
 * The same dopefish outline is also found on Mixom-brand duffel-bags.
 * The "Intimacy is Best" rune bears a strong resemblance to the dopefish.

Doom Eternal

 * The chainsaw is identified as a "Mixom Bucktooth Dopesaw", with an etching of the dopefish as its logo on the chainsaw's guide bar.
 * One of the books in the Fortress of Doom is entitled "From Nopefish to Dopefish: A Dope Tale".
 * Three dopefish, accurate in size as depicted in Commander Keen, can be found in the Cultist Base. The first is hanging from a rope, the second is stuck in a cracked ice wall, and the third is placed on an altar in a little evil shrine.
 * Many brands of candies and snacks use the dopefish as their mascot, including "Fruitchoos", "Dope-Chan", "Okasushi!", and "Dopenuts!".

Community mods

 * Depicted on a wall in E3M7 of Doom the Way id Did.
 * The dopefish appears as a boss monster in MAP32 of Doom 2 the Way id Did.
 * Found on a wall in Z1M4 of Knee-Deep in ZDoom.
 * Referenced in E3M2 of ZPack.
 * The "Dopefish lives!" message is seen on a graffiti in MAP12 of Hellcore 2.0.
 * The "last Dopefish" is displayed at the mutant zoo in MAP04 of Harmony.
 * Dopefish replaces Commander Keen in Doom Zero's MAP11.
 * Depicted on a floor in the secret room in E1M9 of REKKR.